Hydraulic drive system

ABSTRACT

A hydraulic drive system that does not cause a decrease in efficiency of actuators, does not hinder an optimal action of devices such as flow adjustment valves, and does not cause any corrosion of water acting as an operating fluid. The system uses water as an operating fluid. The system includes a hydraulic generation apparatus  40  including, a main tank  41,  a return path  52,  an accessory tank  54 , and a water disposal apparatus  56  disposed in a path  57.  The operating fluid from structuring devices of the processing apparatuses  10, 20  and  30  flows through the return path  52.  The operating fluid flows from the accessory tank  54  to the main tank  41  through the path  57  and the water disposal apparatus  56.

FIELD OF THE INVENTION

[0001] The present invention relates to a hydraulic drive system usingwater such as tap water or the like as an operating fluid. Moreparticularly, the present invention relates to a hydraulic drive systemsuitable for feeding water as an operating fluid to a processingapparatus of a hydraulic drive type and to a drive system for drivingthe processing apparatus.

RELATED ARTS

[0002]FIG. 1 is a diagram showing a configuration of a conventional-typehydraulic drive system and, in particular, showing an example in whichthe hydraulic drive system is applied to a food processing apparatus.The food processing apparatus of a hydraulic drive type shown thereincomprises a plurality (three in this drawing) of processing apparatuses10, 20 and 30, each for processing food, and a hydraulic generationapparatus 40 for feeding high pressure water for driving the processingapparatuses 10, 20 and 30.

[0003] The processing apparatus 10 is provided with hydraulic motors 11and 11, two-way directional control valves 12 and 12 as well as flowadjustment valves 13 and 13. The processing apparatus 20 is providedwith hydraulic cylinders 21 and 21, a directional control valve 22 andcheck valve-mounted flow adjustment valves 23, 23, 23 and 23. Further,the processing apparatus 30 is provided with a hydraulic cylinder 31, ahydraulic motor 32, a hydraulic servo valve 33, a two-way directionalcontrol valve 34 and a flow adjustment valve 35. The high-pressure watergenerated by the hydraulic generation apparatus 40 is fed to each of theprocessing apparatuses 10, 20 and 30 through a feed path 51, and returnwater from the processing apparatuses 10, 20 and 30 is fed to the maintank 41 of the hydraulic generation apparatus 40 through a return path52. The water pressure (back pressure) of the return water of theprocessing apparatuses 10, 20 and 30 may be measured with pressuregauges Pt1, Pt2 and Pt3, respectively.

[0004] A number of hydraulic drive systems of this kind are eachtypically arranged, as shown in FIG. 1, so as for one hydraulicgeneration apparatus 40 to drive a plurality of the processingapparatuses 10, 20 and 30. In these systems, the hydraulic generationapparatus 40 is often disposed in the position remote from each of theprocessing apparatuses 10, 20 and 30 so that water may have to becirculated between the processing apparatuses 10, 20 and 30 as well asthe hydraulic generation apparatus 40 through the feed path 51 and thereturn path 52, each composed of a long hose.

[0005] If the distance L between each of the processing apparatuses 10,20 and 30 and the hydraulic generation apparatus 40 would become long,resistance (back pressure) within the return path 52 for returning waterfrom each of the processing apparatuses 10, 20 and 30 to the hydraulicgeneration apparatus 40 may become so great that an efficiency of anactuator such as the hydraulic cylinders 21 and 31 as well as thehydraulic motors 11 and 32, each constituting each of the processingapparatuses 10, 20 and 30, may be decreased and that the optimal actionsof the devices including the flow adjustment valves 13 and 35 as well asthe check valve-mounted flow adjustment valve 23 may be damaged.Examples that may adversely affect the action of the device may includean example in which the elongation of the return path 52 elevates thepressure of the return port and consequently reduces responsiveness ofthe hydraulic servo valve 33 or decreases the static bearing effects,thereby hindering the behavior and performance of the hydraulic servovalve 33.

[0006] Further, for the hydraulic motors 11 and 32, the inner pressureof the shaft seal is caused to rise as the pressure of the return portbecomes high, thereby leading to the shortening of the life of the shaftseal. Moreover, in the actual system, the distance between the hydraulicgeneration apparatus 40 and each of the processing apparatuses 10, 20and 30 is not necessarily identical to each other, so that theperformance of each apparatus may be caused to differ from each other ifthe processing apparatuses 10, 20 and 30 are driven.

[0007] In addition to the above problems, the use of water as anoperating fluid may cause the problem in which water in the main tank 41of the hydraulic generation apparatus 40 is caused to corrode. Water maycorrode in a pipe of the feed path 51 and the return path 52 between thehydraulic generation apparatus 40 and the processing apparatuses 10, 20and 30, if water is not circulated for a long period of time. Forexample, for a food processing machine that puts an importanceparticularly upon safety and public hygiene, processed products have tobe discarded if a corrosive water as an operating fluid would leakoutside and such water would be attached to the food in the process ofprocessing.

SUMMARY OF THE INVENTION

[0008] With the above situation taken into account, the presentinvention has been completed with the object to provide a hydraulicdrive system that does not reduce efficiency of an actuator such as ahydraulic cylinder, a hydraulic motor, and so on, each constituting aprocessing apparatus, and that does not hinder the optimal actions ofthe devices such as flow adjustment valves and so on, due to anelongation of the distance between the processing apparatus and thehydraulic generation apparatus and a consequential increase inresistance (back pressure) in the return path.

[0009] Further, the present invention has another object to provide ahydraulic drive system suitable as a system for driving a foodprocessing apparatus that causes corroding water to be used as anoperating fluid and puts the greatest importance particularly uponsafety and public hygiene.

[0010] In order to achieve the objects, the present invention provides ahydraulic drive system using water as an operating fluid, comprising aprocessing apparatus for processing an object and a hydraulic generationapparatus for generating a high-pressure water for driving theprocessing apparatus, wherein the hydraulic generation apparatus isprovided with a main tank, an accessory tank is provided in a returnpath through which the operating fluid flows from a processingapparatus-structuring device at the side of the processing apparatus,and a water disposal apparatus is provided in a path through which theoperating fluid flows from the accessory tank to the main tank.

[0011] By locating the accessory tank in the return path through whichthe operating fluid flows from the device structuring the processingapparatus in the manner as described above, the pressure in the returnpath of the structuring device can be sustained at a low level even ifthe distance between the processing apparatus and the hydraulicgeneration apparatus would become elongated. Therefore, a decrease in anefficiency of the actuator such as the hydraulic cylinders, thehydraulic motors and so on, as the devices structuring the processingapparatus, can be prevented. Further, there can be prevented anoccurrence of the hindrance of the optimal action of the devices such asthe flow adjustment valves and so on, including, for example, a decreasein responsiveness of the hydraulic servo valve, a decrease in the staticbearing effects, a decrease in the behavior and performance of thehydraulic servo valve, a shortening of the life of the shaft seal of thehydraulic motor, and an occurrence of different performance among theplural processing apparatuses.

[0012] Moreover, the water disposal apparatus is disposed in the paththrough which the operating fluid flows from the accessory tank to themain tank, so that water as the operating fluid from the processingapparatus can be processed with the water disposal apparatus, therebysustaining the water as the operating fluid in a state suitable for thedrive system.

[0013] The present invention is characterized in that the water disposalapparatus of the hydraulic drive system as described in claim 1 isfurther provided with one or both of a cleaning processing function forcleaning the operating fluid and a sterilizing function for killingmicroorganisms in the operating fluid.

[0014] As the water disposal apparatus is provided with one or both ofthe cleaning processing function for cleaning the operating fluid andthe sterilizing function for sterilizing microorganisms in the operatingfluid, the water acting as the operating fluid from the processingapparatus can be sustained in a clean state or in a germ-free state or aclean and germ-free state. Therefore, the present invention can providea hydraulic drive system suitable as a drive system for a foodprocessing apparatus that puts the most importance on safety andsanitation in the manner as described above.

[0015] The hydraulic drive system according to the present inventioncomprises a high-pressure liquid generating apparatus (40), a main tank(41) communicating with a liquid inlet of the high-pressure liquidgenerating apparatus, an accessory tank (54) with an side exposed toambient atmosphere, a liquid processing apparatus (56), a high-pressureliquid feed path (51) communicating a high-pressure liquid outlet of thehigh-pressure liquid generating apparatus with a high-pressure liquidinlet of the processing apparatus, a first return path (52)communicating a liquid outlet of the processing apparatus with theaccessory tank, a second return path (53) communicating the accessorytank with the liquid processing apparatus, and a third return path (57)communicating the liquid processing apparatus with the main tank.

[0016] The liquid processing apparatus is provided with one or both of afunction of cleaning a liquid and a sterilizing function for sterilizingmicroorganisms in the liquid. The liquid is water. The processingapparatus is for processing food, and the second return path (53) isprovided with a pump (55) for transferring the liquid of the accessorytank to the liquid processing apparatus.

[0017] The food processing plant of the present invention comprises afood processing apparatus (10, 20, 30) drivable with a high-pressureliquid, a high-pressure liquid generating apparatus (40), a main tank(41) communicating with a liquid inlet of the high-pressure liquidgenerating apparatus, an accessory tank (54) with an side exposed toambient atmosphere, a liquid processing apparatus (56), a high-pressureliquid feed path (51) communicating a high-pressure liquid outlet of thehigh-pressure liquid generating apparatus with a high-pressure liquidinlet of the food processing apparatus, a first return path (52)communicating a liquid outlet of the processing apparatus with theaccessory tank, a second return path (53) communicating the accessorytank with the liquid processing apparatus, and a third return path (57)communicating the liquid processing apparatus with the main tank.

[0018] The liquid processing apparatus of the food processing plant isprovided with one or both of a function of cleaning a liquid and asterilizing function for sterilizing microorganisms in the liquid. Theliquid is water and the second return path (53) is provided with a pump(55) for transferring the liquid of the accessory tank to the liquidprocessing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a diagram showing an example of the configuration of ahydraulic drive system of a conventional type.

[0020]FIG. 2 is a diagram showing an example of the configuration of ahydraulic drive system according to the present invention.

[0021] In the drawings, reference numerals denote the following:

[0022]10: Processing apparatus

[0023]20: Processing apparatus

[0024]30: Processing apparatus

[0025]40: Hydraulic generation apparatus

[0026]41: Main tank

[0027]51: Feed path

[0028]52, 53: Return path

[0029]54: Accessory tank

[0030]55: Forced feed pump

[0031]56: Water disposal apparatus

[0032]57: Path

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] Now, a description will be made regarding modes for carrying outthe invention with reference to the accompanying drawings. FIG. 2 is adiagram showing an example of the configuration of the hydraulic drivesystem according to the present invention. As shown in FIG. 2, ahydraulic generation apparatus 40 is provided with a main tank 41. Anaccessory tank 54 is disposed between a return path 52 and a return path53. A water disposal apparatus 56 is disposed in a path 57 through whichwater acting as an operating fluid flows from the accessory tank 54 tothe main tank 41.

[0034] The above configuration of the processing apparatuses 10, 20 and30 may be identical to or different from the configuration of theprocessing apparatuses 10, 20 and 30 as illustrated in FIG. 1. Further,FIG. 2 illustrates an example in which three of the processingapparatuses are used; however, it should be noted herein that the numberof the processing apparatuses is not restricted to this particular oneand that the number of the processing apparatuses can be more than threeor less than three.

[0035] By locating the accessory tank 54 in the return path 52 at theside of the processing apparatuses 10, 20 and 30 in the manner asdescribed above, the accessory tank 54 can be disposed so as to beexposed to ambient atmosphere, so that the pressure of the hydraulicdevices such as the actuators, the flow adjustment valves and so on ofthe processing apparatuses 10, 20 and 30 in the return path 52 can besustained at a low level. Therefore, the actuators such as thecylinders, hydraulic motors and so on can be driven under conditionsthat do not reduce its durability, and the various devices such as thehydraulic servo valves and so on can be operated in an optimal state.

[0036] Further, the path 57 ranging from the accessory tank 54 to themain tank 41 is provided with a forced feed pump 55 for feeding water inthe accessory tank 54 to the main tank 41 of the hydraulic generationapparatus 40 in a pressurized way and further with the water disposalapparatus 56. Therefore, a degree of cleanliness of the water can bemaintained as the operating fluid. Moreover, as the water disposalapparatus 56 can also be configured as a sterilizing apparatus,microorganisms in the operating fluid can also be sterilized, therebyproviding a hydraulic drive system of a hygienic type, which uses wateras an operating fluid. The sterilizing apparatus may include, forexample, an ultraviolet sterilizing apparatus.

[0037] Moreover, the sterilizing apparatus may generally vary itssterilizing effects with a flow rate or a processing time of a liquid tobe treated, which flows through the sterilizing apparatus. The provisionof the sterilizing apparatus in the path 57 between the accessory tank54 and the main tank 41 allows various combinations of the flow rateswith the processing durations of time, thereby enabling the easyselection of the sterilizing apparatus. Specifically, the return path 52from each of the processing apparatuses 10, 20 and 30 to the hydraulicgeneration apparatus 40 can be provided with the. sterilizing apparatus.For example, one sterilizing apparatus can be disposed for two of theprocessing apparatuses. A variation in the combinations of thesterilizing apparatuses with the processing apparatuses allows an easymanagement of the flow rate and the duration of time of the passingwater in order to achieve the optimal sterilization effects of thesterilizing apparatuses.

[0038] In addition, the pressure from the accessory tank 54 to the maintank 41 imposes no adverse influence upon the performance of thehydraulic drive system, so that a water disposal apparatus having arelatively large resistance can also be used. For example, there may beused the water disposal apparatus of a hollow fiber filter type, activecarbon filter type, and so on. They can be arranged in a series in thepath 57.

[0039] In the above example, a separate description has been maderegarding the water disposal apparatus having the cleaning function forcleaning water as the operating fluid and the sterilizing apparatushaving the sterilizing function for killing microorganisms in the water.It is to be noted herein, however, that one apparatus can also be usedwhich has both the cleaning function and the sterilizing function. As amatter of course, the water disposal apparatus can also be combined withthe sterilizing apparatus into one water disposal apparatus having bothof the cleaning function and the sterilizing function as a whole.

[0040] The present invention according to the examples as describedabove enables the configuration of a hydraulic drive system using watersuch as tap water or the like as an operating fluid, which has a highlevel of safety and sanitation as well as can prevent a decrease in theperformance of system-structuring devices.

EFFECTS OF THE INVENTION

[0041] As described above, the invention as described in each of theclaims can offer the remarkable effects as will be describedhereinafter.

[0042] In accordance with the invention, the arrangement of theaccessory tank in the return path of the devices structuring theprocessing apparatuses through which the operating fluid flows from theprocessing apparatus-structuring devices can sustain the pressure in thereturn path at a low level, even if the distance between the processingapparatus or apparatuses and the hydraulic generation apparatus wouldbecome longer. Therefore, a decrease in efficiency of the actuators,such as the hydraulic cylinders, the hydraulic motors and so on,structuring the processing apparatus can be prevented, and a decrease inthe static bearing effects can also be prevented. Moreover, a decreasein the behavior and performance of the hydraulic servo valve can beprevented. In addition, the lowering of the life of the shaft seal ofthe hydraulic motor can be prevented, and an occurrence of a differencein the performance among the plural processing apparatuses can also beprevented.

[0043] Further, the path for the operating fluid flowing from theaccessory tank to the main tank is provided with the water disposalapparatus, so that the water from the processing apparatus acting as theoperating fluid can be treated with the water disposal apparatus.Therefore, the water as the operating fluid can be sustained in a statesuitable for use with a drive system.

[0044] In accordance with the invention, the water disposal apparatus isprovided with one or both of the cleaning function for cleaning theoperating fluid and the sterilizing function for sterilizingmicroorganisms in the operating fluid. Therefore, the water from theprocessing apparatus acting as the operating fluid can be maintained ina clean state or in a germ-free state or in a clean and germ-free state,thereby providing a hydraulic drive system suitable particularly for afood processing apparatus that has to put the most importance uponsafety and public hygiene.

1. A hydraulic drive system for driving a processing apparatus (10, 20,30), comprising a high-pressure liquid generating apparatus (40), a maintank (41) communicating with a liquid inlet of the high-pressure liquidgenerating apparatus, an accessory tank (54) with an side exposed toambient atmosphere, a liquid processing apparatus (56), a high-pressureliquid feed path (51) communicating a high-pressure liquid outlet of thehigh-pressure liquid generating apparatus with a high-pressure liquidinlet of the processing apparatus, a first return path (52)communicating a liquid outlet of the processing apparatus with theaccessory tank, a second return path (53) communicating the accessorytank with the liquid processing apparatus, and a third return path (57)communicating the liquid processing apparatus with the main tank.
 2. Thehydraulic drive system as claimed in claim 1, wherein the liquidprocessing apparatus is provided with one or both of a function ofcleaning a liquid and a sterilizing function for sterilizingmicroorganisms in the liquid.
 3. The hydraulic drive system as claimedin claim 1 or 2, wherein the liquid is water, the processing apparatusis for processing food, and the second return path (53) is provided witha pump (55) for transferring the liquid of the accessory tank to theliquid processing apparatus.
 4. A food processing plant comprising afood processing apparatus (10, 20, 30) drivable with a high-pressureliquid, a high-pressure liquid generating apparatus (40), a main tank(41) communicating with a liquid inlet of the high-pressure liquidgenerating apparatus, an accessory tank (54) with an side exposed toambient atmosphere, a liquid processing apparatus (56), a high-pressureliquid feed path (51) communicating a high-pressure liquid outlet of thehigh-pressure liquid generating apparatus with a high-pressure liquidinlet of the food processing apparatus, a first return path (52)communicating a liquid outlet of the processing apparatus with theaccessory tank, a second return path (53) communicating the accessorytank with the liquid processing apparatus, and a third return path (57)communicating the liquid processing apparatus with the main tank.
 5. Thefood processing plant as claimed in claim 4, wherein the liquidprocessing apparatus is provided with one or both of a function ofcleaning a liquid and a sterilizing function for sterilizingmicroorganisms in the liquid.
 6. The food processing plant as claimed inclaim 4 or 5, wherein the liquid is water and the second return path(53) is provided with a pump (55) for transferring the liquid of theaccessory tank to the liquid processing apparatus.